A network game system which comprises a plurality of game machines each having a server function and a client function, in which the respective game machines operate as clients and at least one game machine also operates as a server, thereby providing a game to be played by the players of a plurality of game machines, is available (for example, in paragraph 0154 of Patent Document 1). For example, in a known network game system, a soccer game is played by the players of two game machines, in which one of the two game machines operating as a client also operates as a server, or a server-client machine, and the other operates solely as a client, or a client-dedicated machine.    Patent Document 1: Japanese Patent Laid-open Publication No. 2003-225469
In this network game system, the client-dedicated machine executes the game while exchanging data with the server-client machine via a communication network, which makes the client-dedicated machine inferior in terms of ability to respond to game operations, compared to the server-client machine. Consequently, the player of the client-dedicated machine is forced to play the game in a disadvantageous situation compared to the player of the server-client machine. The network game system providing the soccer game as described above addresses this problem by assigning the role of a server to a different game machine between the first and second halves of the game.